Structural isomerization of synephrine influences its uptake and ensuing glutathione depletion in rat-isolated cardiomyocytes

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Luciana Grazziotin Rossato (Author) Other; Vera Marisa Costa (Author) Other; de Pinho, PG (Author) FFUP; Felix Carvalho (Author) FFUP; Maria de Lourdes Bastos (Author) FFUP; Fernando Remiao (Author) FFUP

Journal

Title: Archives of Toxicology

Vol. 85

Pages: 929-939

ISSN: 0340-5761

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 23 Citations

Scopus - 26 Citations

Scientific classification

FOS: Medical and Health sciences > Basic medicine

Other information

Authenticus ID: P-002-P8M

DOI: 10.1007/s00204-010-0630-9

Abstract (EN): Synephrine is a natural compound, frequently added to ephedra-free dietary supplements for weight-loss, due to its effects as a nonspecific adrenergic agonist. Though only p-synephrine has been documented in plants, the presence of m-synephrine has also been reported in weight-loss products. The use of synephrine in dietary supplements was accompanied by reports of adverse effects, especially at the cardiovascular level. It is well known that the imbalance in cardiac glutathione levels can increase the risk of cardiomyopathy. The present work aimed to study the role of organic cation-mediated transport of m- and p-synephrine and the possibility that p- and m-synephrine induce intracellular changes in glutathione levels in calcium-tolerant freshly isolated cardiomyocytes from adult rat. After a 3 h incubation with 1 mM p- or m-synephrine, the intracellular content of synephrine was measured by gas chromatography/ion trap-mass spectrometry (GC/IT-MS); cell viability and intracellular glutathione levels were also determined. To evaluate the potential protective effects of antioxidants against the adverse effects elicited by m-synephrine, cells were pre-incubated for 30 min with Tiron (100 mu M) or N-acetyl-cysteine (NAC) (1 mM). To assess the influence of alpha(1)-adrenoceptors activation in glutathione depletion, a study with prazosin (100 nM) was also performed. The results obtained provide evidence that organic cation transporters OCT3 and OCT1 play a major role in m- and p-synephrine-mediated transport into the cardiomyocytes. The importance of these transporters seems similar for both isomers, although p-synephrine enters more into the cardiomyocytes. Furthermore, only m-synephrine induced intracellular total glutathione (GSHt) and reduced glutathione (GSH) depletion. NAC and Tiron were able to counteract the m-synephrine-induced GSH and GSHt decrease. On the other hand, the incubation with prazosin was not able to change m-synephrine-induced glutathione depletion showing that this effect is independent of alpha(1)-adrenoceptor stimulation. In conclusion, both positional isomers require OCT3 and OCT1-mediated transport to enter into the cardiomyocytes; however, the hydroxyl group in the p-position favours the OCT-mediated transport into cardiomyocytes. Furthermore, the structural isomerization of synephrine influences its toxicological profile since only m-synephrine caused GSH depletion.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11